Absolutely.
These days I vape unflavored, but occasionally I'll mix some of my already-flavored juice (I have a lot still on-hand from when I was vaping pre-mixed juices) with some of my unflavored. I'm not a cloudchaser or a flavorchaser. I just need ma fix, man.
Go for it, although be careful about over-diluting if you're not used to the taste of unflavored. Test before you commit, for sure. It does have a.. Lubricant-y... Vaseline-y... Sorta taste.